Calutron receivers



Dec. 6, 1955 s. w. BARNES CALUTRON RECEIVERS 3 Sheets-Sheet 1 Filed Jan. 9, 1946 INVENTOR. S/DNEYWBARNES ATTORNEY.

Dec. 6, 1955 s. w. BARNES 2,726,336

CALUTRON RECEIVERS Filed Jan. 9, 1946 3 Sheets-Sheet 2 2 97 INVENTOR. SIDNEY W BARNES BY M ATTORNEY.

D 1955 s. w. BARNES CALUTRON RECEIVERS 3 Sheets-Sheet 3 Filed Jan. 9, 1946 INVENTOR SIDNEY W BARNES ATTORNEY.

United States Patent CALUTRON RECEIVERS Sidney W. Barnes, Rochester, N. Y., assignor to the United States of America as represented by the United States Atomic Energy Commission Application January 9, 1946, Serial No. 640,103

8 Claims. (Cl. 250-413) The general subject of this invention involves the separation, based on difference in mass, of minute particles, such as atoms, and especially the separation of isotopes of an element, or the separation of a portion of an element enriched with respect to a particular isotope on a scale yielding commercially useful quantities of the collected material.

The type of means or mechanism to which the invention relates is known as a calutron, and correspondingly the method or process is known as a calutron method or process. For a complete disclosure of a calutron and its mode of operation, reference is made to the copending application of Ernest 0. Lawrence, Serial No. 557,784, filed October 9, 1944, for Methods of and Apparatus for Separating Materials, now Pat. No. 2,709,222.

The presently preferred form of the calutron comprises an evacuated tank disposed between the poles of an electromagnet so that the evacuated space within the tank is pervaded with a magnetic field of high flux density. Within the tank there is provided a source unit? that includes means for supplying the polyisotope as a vapor or gas to an ionizing region, ionizing apparatus for producing positively ionized particles from the vapor, and an accelerating device maintained at a high negative electrical potential with respect to the ionizing apparatus for withdrawing the positive ions and imparting to each of them a predetermined energy in the form of substantially uniform velocities along paths generally normal to the direction of the magnetic field from a line virtual focus toward an elongated beam defining slit in the accelerating device disposed generally parallel to the direction of the magnetic field.

After passing through the beam defining slit, the accelerated ions continue to move transversely to the magnetic field and are constrained to travel along substantially arcuate paths having radii that vary with the masses of the particles (within a magnetic field of uniform intensity). By virtue of the accelerating slit construction, the paths for the ions of a given mass diverge from a median path to an extent determined by the geometry of the ionizing and accelerating devices and by such inhomogeneity as may exist in the magnetic field through which the ions travel. This divergence of the paths of travel of the ions of a given mass continues through the first 90 of arcuate travel from the virtual focus at the source unit, and then the paths converge during the next 90 and cross each other in a region of focus approximately 180 from the virtual focus. Thus, in effect, geometrical focusing of a ribbon-shaped stream of ions of a given mass is accomplished adjacent the 180 point, even though there is a relatively wide initial angle of divergenceof the ions. Likewise, the ions of any other given inass travel along paths that define a ribbon-shaped stream coming to a similar focus approximately 180 from the virtual focus at the source unit.

A receiver is disposed within the vacuum tank adjacent the 180 foci of the isotope ions to be separated, for de- 'ice 2 ionizing them and for separately collecting material from one or all of them as may be desired. 7

The paths of a stream of ions of a given mass do not all cross precisely at a 180 line focus, and the cross sectional area of the stream of ions at the region of sharpest focus thereof would normally have an elongated rectangular configuration of substantial width, the width varying with the angular divergence of the ions at the source. The quantity of material transmitted in the beam also varies with the angular divergence at the source, and, with streams of ions of the heavier elements, a practical minimum divergence for collecting commercial quantities of material produces 180 foci of such width that they overlap considerably. Thus, in practice, the quantities of material collectable at the receiver from one ion stream contain some material from the adjacent ion stream and are merely enriched with respect to a particular isotope.

When employing a uniform magnetic field within the calutron tank, the separation of ions of different isotopes having the same initial angular divergence is dependent solely upon the mass difference ofthe ions, and they are spaced apart at their respective 180 foci by an amount approximately equal to the difierence in the diameters of their respective paths. By reducing the divergence of the beam at the beam defining slit, the widths of the respective 180 foci of streams of ions of different isotopes may be reduced and the amount of overlap of these foci correspondingly reduced. However, since the amount of material transmitted in the beam varies with the angular divergence at the source, the amount of overlapping of the 180 foci of streams of ions of different isotopes increases (and the obtainable degree of enrichment of collected material witlirespect to a particular isotope decreases) as the amount of material transmitted in' the beam is increased. As a result, a compromise was originally required between maximum production and maximum enrichment.

In order to increase the quantity of material transmitted in an ion beam without reducing the isotopic enrichment of the collected material, the shape or configuration of the beam may be modified by means of specially contoured bodies of magnetically permeable material that are introduced into the calutron tank to cause predetermined variations in the magnetic field along the path of the beam. Such magnetically permeable bodies are referred to as magnetic shims, and the resulting modified beam is referred to as a mag netically shimmed beam or a shimmed beam. In a copending application of Julius Robert Oppenheimer et al., Serial No. 637,690, filed December 28, 1945, .an arrangement of magnetic shims is disclosed, and the configuration of the modified beam resulting from the use of the shims is illustrated and described in some detail. As disclosed in that application, the modification of the beam is such that the normally elongated, rectangular, 180 focal pattern of each beam component is compressed along one side, is extended along the opposite side, and, in addition, is curved to produce what may be termed a gull-wing pattern. v

By modifying the 180 focal patterns in this manner, the average width of the pattern for each isotope ion stream is reduced, and the length thereof is'increased,

' whereby the amount of overlapping of the streams of different isotopes is substantially reduced for any given initial angular divergence at the source. This permits increasing the amount of material arriving at the foci of the streams of different isotopes by employing a greater angular divergence at the source withoutcon taminating the material arriving at one 180 focus with material arriving at the adjacent overlapping focus to nearly the extent formerly resulting when a magnetic field of substantially uniform intensity was employed.

However, a study of the locations of the 180 foci of maximum sharpness in streams of ions of different isotopes has revealed that the above described modification of the magnetic fieid causes a relative shifting of the foci along the general direction of travel of the beam at the 180 region of focus. :It is desirable that a receiver viewing face, that defines the selected portions of the two components of a beam to be received, pass through the most intense portions of the foci of both of the beam components. As a result, the receivers heretofore employed, having a beam viewing face disposed in a plane normal to the general direction of travel of the beam at the 180 region of focus, are unsatisfactory for most efficient separation of the streams of ions of different isotopes.

Other expedients for achieving greater separation of the fooi of streams of ions of different isotopes have been employed, whereby the paths of the ions are modified after the ions have been accelerated and whereby the foci of different isotopes are relatively offset along the general direction of travel of the beam at the 180 region of focus. A beam so modified by the use of other expedients is also intended to be included within the meaning of the term shimmed beam as employed herein, whether the expedients depend in whole or in part upon electromagnetic influences, electrostatic influences, or combinations thereof.

It is an object of the present invention to provide an improved calutron receiver adapted to separate with maximum efficiency the isotope components of a shimmed ion beam.

Another object of the invention is to provide a calutron receiver adapted to collect a maximum proportion of one isotope component of a shimmed ion beam.

Another object of the invention is to provide a calutron of the shimmed beam type having a receiver disposed therein for separating with maximum efficiency the isotope components of the beam.

Other objects and advantages of the invention will become apparent from the following detailed description of a preferred embodiment thereof and from the accompanying drawings in which:

Figure l is a horizontal sectional view of a calutron tank, showing the arrangement of the source and receiver within the tank and the relation of the tank to the magnet, certain parts being shown somewhat schematically for simplicity;

Fig. 2 is a horizontal sectional view on an enlarged scale of the receiver shown in Fig. 1, the plane of the section being taken horizontally through the center of the receiver;

Fig. 3 is a vertical sectional view of the receiver shown in Fig. 2, the plane of the section being indicated by the line 33 in Fig. 2; and

Fig. 4 is another vertical sectional view of the receiver shown in Fig. 2, the plane of the section being indicated by the line 4-4 in Fig. 2.

Referring to the drawings, Fig. 1 illustrates a calutron of the general character disclosed in the Lawrence appli cation, mentioned above, but embodying certain modifications including, among other features, a receiver constructed in accordance with the present invention for receiving a magnetically shimmed ion beam. The calutron comprises a C-shaped tank that is supported midway between a pair of horizontally disposed, vertically spaced-apart pole faces 11 (only one being shown) of a calutron magnet, whereby a magnetic field may be created throughout the interior of the tank with the magnetic lines of force passing upwardly therethrough. The tank is adapted to be evacuated through a pumpout conduit 12 to reduce the interior pressure, in a manner disclosed in the above-mentioned Lawrence application, and, for purposes of illustration, may be considered as being provided with magnetic shims (not shown) for modifying an ion beam passing through the tank, in the manner and for the purpose disclosed in the above-mentioned Oppenheimer et al. application.

A source unit, illustrated schematically in Fig. 1 and generally designated 13, is mounted within the tank 10 at one end thereof on one of a pair of removable end walls 14 for producing, from a polyisotopic charge material, a beam of singly ionized positive ions traveling along substantially arcuate paths from a virtual focus at the source to a region of focus approximately along said paths toward the opposite end of the tank. As hcreinber'ore indicated, the source unit is designed to project the ions along paths that are initially divergent to either side of a median path by various angles between predetermined maxima and that later converge toward and diverge beyond a 180 region of focus at angles on either side of a median path dependent upon their respective initial angular divergences and the effects of the distorted magnetic field.

The paths of several ions traveling in a horizontal plane through the center of the beam are schematically and somewhat ideally illustrated in Fig. l by two sets of three lines each, one set of dash lines representing a median path 15 and two extreme paths 16 and 17 of a stream of ions of one isotope, and the other set of solid lines representing a median path 18 and two extremepaths is and 20 of a stream of ions of another heavier isotope. The two streams of ions originate at a line virtual focus 21 having a vertical height (not shown) that is dependent upon characteristics of the source unit extrinsic to the considerations of present interest. The stream of ions represented by the first-mentioned set of lines 15, 16, and 17 converges toward and diverges beyond a focus 22 located approximately 180 from thevirtual focus 2). toward the opposite end of the tank 10, and, similarly, the stream of ions represented by the secondmentioned set of lines 18, i9, and 20 converges toward and diverges beyond a second focus 23 that is laterally spaced from the focus 22 of the ions of a lesser mass. in addition to being laterally spaced apart, the foci 22 and 23 are relatively offset along the general direction of travel of the beam at the 180 region of focus by reason of the effects of the magnetic shims, the precise amount of offset being a function of the resolving power of the shims. For a disclosure of one example of the actual shape of the portions of a shimmed beam comprised by the two streams of ions of the U and U isotopes (ignoring all scattered material), reference is made to the above-mentioned Oppenheimer et al. application.

A receiver, generally designated 25, is mounted on a removable end wall 14 of the C-shaped tank 10, at the opposite end thereof from the source unit 13, for de: ionizing and collecting ions arriving at one of the foci 22 separately from those arriving at the adjacent focus 23, and for trapping ions reaching the first-mentioned teens 22 in such a manner that they can be separately removed from the calutron.

The receiver 25 is mounted on a tube 26 that projects outwardly through an aperture (not shown) in the adjacent end wall 14 of the tank 10. The tube 26 is preferably supported substantially centrally in the aperture in the adjacent end wall, with suificient clearance to avoid electrical contact with the end wall, on apparatus carried by a cylindrical insulator 27 that is secured to the end wall in an air-tight manner with one end thereof surrounding the aperture, the tube preferably being mounted for rotary movement about its own axis, for pivotal movement in both a horizontal and a vertical direction, and for longitudinal movement along its axis, with the outer end or" the tube 26 and the space between the tube and the surrounding walls of the aperture being suitably sealed against leakage of air into the tank. The apparatus for supporting the tube 26 forms no part of the present invention, and one example of suitable r apparatus is disclosed in detail in the above-mentioned 5 Lawrence application. With such apparatus, the inner end of the tube 26 may be rotated and translated in any direction for aligning the receiver 25 with the beam to be received thereby.

The receiver 25 comprises a back plate 30 of rectangular configuration, having a centrally disposed aperture 31 therein. The inner end of the supporting tube 26 is secured to the back plate 34), in coaxial alignment with the aperture 31, by means of a flange 32 that may be soldered to the tube and removably secured to the back plate 30 by suitable fastening elements 33. A housing projects forwardly from the back plate 30 and comprises a pair of oppositely disposed side plates 34 and 35, a top plate 36, and a relatively thin bottom plate 37 that are all suitably secured to each other at their adjoining edges and to the back plate 30.

An angular bracket 38 is secured along the forward edge of the side plate 34, and a laterally projecting flange 39 is secured along the forward edge of the side plate 35 for supporting a row of three stand-off insulators 40 that are disposed in spaced-apart relation along the bracket 38 and a similar row of four stand-off insulators 41 that are disposed in spaced-apart relation along the flange 39. The insulators 40 and 41 provide structure for mounting a face plate 42 generally parallel to the direction of the magnetic field in the tank 10 and inclined at an acute angle to the general direction of travel of the beam at its 180 region of focus. To give another plane of reference, it may also be said that the face plate 42 is inclined at an acute angle :1: to a plane that contains the linear virtual focus at the source unit 13 and is disposed normally to the general direction of travel of the beam at both the virtual focus and the 180 region of focus.

The face plate 42 is provided with a large rectangular opening 43 therethrough that is somewhat greater in its vertical dimension than the vertical height of the 180 foci 22 and 23 of the U and U components of the beam and somewhat greater in its horizontal dimension parallel to the plate than the combined width of these foci. A graphite plate 45 is secured directly to the outer surface of the face plate 42 in any suitable manner and is similarly disposed with respect to the above described reference coordinates for presenting to the beam a surface 46 that will hereinafter be referred to as the viewing face of the receiver.

With the structure disclosed, the viewing face 46 is also disposed at the same angles 0 and 3 with respect to the above described reference coordinates as the face plate 42. As indicated above, the ideal values of 6 and 4; for locating the viewing face 46 in a plane passing through the foci 22 and 23 are dependent largely upon the resolving power of the shims. Practical considerations have limited variations in the resolving power of the shims employed in existing calutron tanks and have correspondingly limited the possible variations in the values of 0 and While the theoretical or ideal values of 6' and q for the shims employed heretofore have been respectively substantially smaller and greater than 45, marked improvement was achieved in the enhancement and volume of material collected when employing the receiver illustrated herein with assumed values of both 0 and equal to 45, an approximation of the theoretical or ideal values that simplifies the design and construction of the receiver.

The graphite plate 45 is provided with an elongated curved slot 47 that is disposed in front of the opening 43 in the face plate 42 and conforms generally to the cross sectional configuration of the beam at the region of focus, but that is somewhat reduced in size in order that the plate will intercept all but a selected portion of maximum ion intensity of the'U and U components of the beam.

To protect the insulators 40 and 41 from becoming coated with electrically conducting material as a result of scattering of beam particles, a shield 48 may be suit- 6 ably secured to the edges of the face plate 42 around its entire periphery.

A graphite electrode 50, comprising an ion intercepting portion 51 and a supporting extension 52, is mounted, in a manner described hereinafter, with the ion intercepting portion 51 projecting into the elongated slot 47 and with the supporting extension 52 disposed generally behind the graphite plate 45. The ion intercepting portion 51 of the electrode 50 extends nearly the full length of the slot 47, terminating just short of the oppositeends thereof, and one side edge 53 of the ion intercepting portion of the electrode is substantially coincident with a curved line extending longitudinally of the slot 47 and midway between its side edges for the entire length of the electrode, while the opposite side edge of the electrode is similarly curved and spaced a small distance from an adjacent side edge of the slot 47 for substantially the full length of the electrode. A portion of the exposed surface of the ion intercepting portion 51 of the electrode lies in the plane of the viewing face 46, and a V-shaped ion trapping trough 54 is provided along the entire length of this surface.

The electrode 50 is adapted to intercept a selected portion of the U component of the beam of greatest ion intensity and to define one side of a U slot 55. within the larger slot 47, through which a selected portion of the U component of the beam of greatest ion intensity may pass, these two portions of the two components of the beam preferably being substantially identical in cross sectional area and configuration.

An ion receiving pocket, generally designated 60, is disposed within the receiver housing and comprises an outer frame 61 formed of metal plates secured together in any suitable manner with one end of the frame open to permit insertion and removal of a liner 62 adapted to be contained within the frame 61. The liner 62 is provided with an elongated, curved opening 63 in the forward wall thereof disposed in alignment with the U3 slot 55 for passing intothe pocket liner 62 substantially all of the ions passing through this slot.

The pocket 60 is mounted within the receiver housing in insulated relation thereto by means of an arrangement of three offset fastening elements 64, 65, and 66 and three offset tubular insulators 67, 68, and 69 in the side wall 34 of the receiver housing. The fastening elements serve to pull the pocket 60 toward the side wall 34 and against the tubular insulators, that are thereby clamped between the pocket frame and the side wall 34, appropriate aligned I grooves being provided in the pocket frame and in the side wall for seating the insulators. The fastening elements 64, 65, and 66 pass through insulator sleeves 70, that are partially counter-sunk into the outer surface of the side wall 34, and through apertures 71 in the side wall 34, the apertures 71 having a somewhat greater diameter than the fastening elements, whereby electrical contact between the fastening elements and the side wall is avoided. In this manner the pocket 60 is electrically isolated from the rest of the receiver and currents thereto may be read by means of an electrical lead 72 extending from a contact 73 on the pocket frame 61 to a rod type conductor 74 that passes out of the calutron through the supporting tube 26, from which it is insulated in any suitable manner (not shown).

The electrode 50 is secured to a plate 75 that is in turn mounted on the adjacent side of the frame 61 of the pocket 60 by means of an arrangement of three oifset fastening elements 76, 77, and 78 and three offset tubularinsulators 79, 80, and 81, similar to the arrangement of fastening elements and insulators with which the pocket 60 is secured to the side wall 34 of the receiver housing. The fastening elements 76, 77, and 78 are likewise provided with cooperating insulator sleeves 82 and pass through oversized openings 83 in the plate 75, whereby they are maintained out of electrical contact with the plate 75 and whereby the plate 75 and the associated electrode 50 are electrically isolated from the pocket 60 and from the rest of the receiver.

For cooling the face plate 42, a cooling fluid line 85 is run into the interior of the receiver housing through the supporting tube 26 and is secured to the back side of the face plate 42 in heat conducting relation thereto substantially completely around the aperture 43 therein, and then extends out of the receiver housing again through the supporting tube 26, whereby a suitable cooling fluid may be circulated through the tube to cool the face plate 42.

For cooling the electrode 50, a cooling fluid line 86 is run into the interior of the receiver housing through 'the supporting tube 26 and is secured to one side of the plate 75, in heat conducting relation thereto, by means of a rod 87 that may be soldered directly to the cooling fluid line and removably secured to the plate 75 by suitable fastening elements 88. From the plate 75, the cooling fluid line 86 continues back out of the receiver housing again through the supporting tube 26, whereby a suitable cooling fluid may be circulated through the tube to cool the plate 75 and the electrode 50 mounted thereon.

By employing an electrically non-conducting cooling fluid, such as distilled water, and by insulating the cooling fluid lines from the supporting tube 26, the cooling fluid lines may serve as electrical leads to the face plate 42 and electrode 50 for measuring the quantity of ions intercepted thereby.

In order to prevent contamination of the interior of the pocket liner 62 during the Warm-up period, before the beam to be received has become stabilized and has been focused for reception, a door 90 is mounted on the forward surface of the face plate 42 by means of a pair of hinges 91 and 92. The door is slightly greater in length than the slot 47 in the graphite plate 45 and is adapted to be swung about the hinges 91 and 92 from a closed position against and substantially covering the viewing face 46, to an open position out of the paths of the U and U components of the beam. For operating the door between its open and closed positions, a rod 93 is pivotally connected at one end to the door by means of a bracket 94 and projects into the interior of the receiver, an aperture 95 being provided in the face plate 42 to permit the rod 93 to be moved generally longitudinally for swinging the door about its hinges. One end 'of a length of heavy wire 96, such as music wire, is suitably secured to the opposite end of the rod 93 and extends therefrom out of the receiver and into the supporting tube 26. A stationary length a of copper tubing or the like 97 surrounds the wire 96 for a considerable portion of its length and is bent to conform to a desired path of travel for the wire, whereby electrical contact between the wire and other parts of the receiver may be avoided. Inside the supporting tube 26, a suitable mechanism (not shown) may be provided, such as that disclosed in the copending application of Edward J. Lofgren, Serial No. 596,222, filed May 28, 1945, for moving the wire 96 Within the tubing 97 to swing the door 90 about its hinges 91 and 92 between open and closed positions.

To facilitate determining when the ion beam is properly focused for most eflicient reception, a series of narrow slots 98 are provided in the door 90 in alignment with the curved longitudinal center line of the ion intercepting portion of the electrode 50 when the door is in its closed position. Thus, when the door 90 is closed, the slots 98 are adapted to pass narrow portions of the ion beam of minimum ion intensity to the electrode 50, and focusing of the ion beam may be accomplished by varying the accelerating voltage of the source unit 13 until the current to the electrode is maximized. For a more detailed description of the purpose and operation of the slotted door structure, reference is made to the above-mentioned Lofgren application.

With the receiver 25 mounted in the evacuated tank '10, with cooling fluid circulating through the cooling fluid lines and 86, and with the door in its closed position, the beam is created and focused in accordance with the current to the electrode 50 that results from the passage of ions thereto through the slots 98 in the door 90. When a proper focus of the beam has been achieved, the door 90 is opened, and subsequent readings of current to the electrode 50 and to the pocket 60 may be observed as a check on general beam conditions and on the rate at which ions are entering the pocket. The door 90 may be closed during a run in the event the condition of the beam should become unsatisfactory, in order to prevent contamination of the material already collected in the pocket 60 while the condition of the beam is being corrected; or the door may be closed at regular intervals during a run to obtain a more reliable check on the accuracy of focus and to carry out any required refocusing operation.

At the conclusion of the run, the beam is cut off, the circulation of cooling fluid through the cooling fluid lines is stopped, the pressure in the tank is brought up to atmosphere pressure, and the receiver is removed from the tank by removing the tank wall 14 on which 'it is mounted. Access to the interior of the receiver is obtained by removing the graphite plate 45 and disconnecting the pocket 60 from the side wall 34 and the plate 75 from the pocket frame 61, after which the pocket may be removed through the aperture 43 in the face plate 42 for recovery of material deposited therein.

What is claimed is:

1. In a calutron including means for producing a magnetic field and means disposed within said magnetic field for projecting ions of a polyisotopic material transversely through said magnetic field as a ribbon-like beam charac terized by divergence of streams of ions of different mass during travel thereof to respective foci of maximum sharpness that are disposed within said magnetic field and are relatively offset along a median path of the beam, a receiver comprising a beam viewing face containing a beam delimiting slot and an ion intercepting electrode surface, said beam delimiting slot and said electrode surface being similarly offset, and an ion receiving pocket disposed behind said viewing face in alignment with said slot for deionizing and collecting ions passing therethrough.

2. In a calutron including means for producing a magnetic field and means disposed within said magnetic field for projecting ions of a polyisotopic material transversely through said magnetic field as a ribbon-like beam characterized by divergence of streams of ions of different mass during travel thereof to respective foci of maximum sharpness that are disposed within said magnetic field and are relatively ofiset along a median path of the beam, a receiver comprising a beam viewing face containing a beam delimiting slot and a contiguous ion intercepting surface, said slot and said surface being disposed, in a plane passing through said foci, and an ion receiving pocket disposed behind said viewing face in alignment with said slot for deionizing and collecting ions passing therethrough.

3. In a calutron including means for producing a magnetic field and means disposed within said magneitc field for projecting ions of a polyisotopic material transversely through said magnetic field as a ribbon-like beam characterized by divergence of streams of ions of different mass during travel thereof along arcuate paths from a virtual line focus adjacent their source to respective foci of maximum sharpness disposed within said magnetic field approximately along said median path from said line focus and in relatively offset relation along a median path of the beam, a receiver comprising a beam viewing face disposed at an oblique angle with respect to a plane that contains said line focus and that is disposed normal to said median path adjacent said 180 foci.

4. In a calutron of the shimmed beam type including a receiver having a viewing face disposed in the path of the beam for defining a beam delimiting slot, and an ion receiving pocket disposed behind said viewing face for deionizing and collecting ions passing through said slot, means normally supporting the viewing face of the receiver at a predetermined oblique angle with respect to a median path of the beam where it intersects the viewing face.

5. In a calutron of the shimmed beam type including a receiver having a viewing face disposed within a magnetic field in the path of the beam for defining a beam delimiting slot, and an ion receiving pocket disposed behind said viewing face for deionizing and collecting ions passing through said slot, means normally supporting the viewing face of the receiver parallel to said magnetic field and obliquely with respect to the direction of a median path of the beam where it intersects the viewing face.

6. In a calutron of the shimmed beam type including a receiver having a viewing face disposed in the path of the beam for defining a plurality of ion receiving areas, and an ion receiving pocket disposed behind said viewing face in alignment with one of said areas for deionizing and collecting ions arriving within the aligned area, means normally supporting the viewing face of the receiver with said ion receiving areas relatively offset a predetermined distance along a median path of the beam.

7. In a calutron of the shimmed beam type including a receiver having a viewing face disposed in the path of the beam for defining a beam delimiting slot and an adjacent ion intercepting area, and an ion receiving pocket disposed behind said viewing face for deionizing and collecting ions passing through said slot, means normally supporting the viewing face of the receiver with said slot and said ion intercepting area relatively offset a predetermined distance along a median path of the beam.

8. In a receiver for a calutron of the shimmed beam type wherein ions of a polyisotopic material are projected in diverging and curving paths through a magnetic field to attain mas separation and the ions of each mass arrive at separate points of focus as beams, the combination comprising a housing having an open side, a closure member for said open side mounted on said housing in insulated relation thereto and having a slot of suflicient width to pass at least two of said masses of ions at the foci thereof, supporting structure for said housing to dispose the slot of said closure member at the foci of at least two of said masses of ions, a collecting electrode disposed within and insulated from said housing to receive the ions of one mass passing through said slot, and an enclosed collecting pocket disposed within said housing and insulated therefrom, said pocket having an aperture disposed in alignment with said slot to receive and retain ions of a second mass.

References Cited in the file of this patent UNITED STATES PATENTS 2,354,122 Hipple, Jr July 18, 1944 2,417,797 Hipple, Ir Mar. 18, 1947 2,427,484 West Sept. 16, 1947 2,447,260 Martin Aug. 17, 1948 

1. IN A CALUTRON INCLUDING MEANS FOR PRODUCING A MAGNETIC FIELD AND MEANS DISPOSED WITHIN SAID MAGNETIC FIELD FOR PROJECTING IONS OF A POLYISOTOPIC MATERIAL TRANSVERSELY THROUGH SAID MAGNETIC FIELD AS A RIBBON-LIKE BEAM CHARACTERIZED BY DIVERGENCE OF STREAMS OF IONS OF DIFFERENT MASS DURING TRAVEL THEREOF TO RESPECTIVE FOCI OF MAXIMUM SHARPNESS THAT ARE DISPOSED WITHIN SAID MAGNETIC FIELD AND ARE RELATIVELY OFFSET ALONG A MEDIAN PATH OF THE BEAM, A RECEIVER COMPRISING A BEAM VIEWING FACE CONTAINING A BEAM DELIMITING SLOT AND AN ION INTERCEPTING ELECTRODE SURFACE, SAID BEAM DELIMITING SLOT AND SAID ELECTRODE SURFACE BEING SIMILARLY OFFSET, AND AN ION RECEIVING POCKET DISPOSED BEHIND SAID VIEWING FACE IN ALIGNMENT WITH SAID SLOT FOR DEIONIZING AND COLLECTING IONS PASSING THERETHROUGH. 